We found this specimen of short-tailed weasel or ermine ( Mustela erminea) at Slough Creek, Yellowstone National Park (dead of unknown causes). Besides the shorter tail, ermine are white rather than buff underneath. The feet are white and a third of the tail is black.
Ermine effective predators of mice, voles, shrews, pocket gophers, pikas, and even rabbits. They often take over the burrows of mice, ground squirrels, or chipmunks.
Winter is a good time to track the ermine. The short-long-short-long pattern is distinctive.
In the photo below, a marten makes an an interesting transition. The photo next to it compares ermine tracks with a pine marten I found along the North Fork of the Flathead in Glacier National Park.
